Diseases caused by helmintic parasite infections far outnumber diseases caused by other infectious agents. It is estimated that one billion people are infected with roundworm alone and that eight hundred million people are infected with hookworm. This does not include infections caused by other helmintic parasites nor include the millions and perhaps billions of animals infected with helmintic parasites. The taxonomic, identification, classification, and history of helmintic parasites and the epidemiology, treatment, and conduct of the more prevalent parasitic infections is reviewed in Parasitology for Veterinarians by J. R. Georgi, W. B. Sanders Co., 3rd edition (1980).
Attempts to control helmintic parasites are disclosed in ancient Chinese and Egyptian writings dating back 3500 years. More recently, there has been a continuing effort to develop methods for treating infected animals and controlling the spread of helmintic parasite infections. Broad spectrum anthelmintic agents such as aminoglycoside antibodies, organophosphorous compounds, benzimidazoles, organic arsenic compounds, piparazines, imidoylureas are a few among many anthelmintic agents that have been used to treat and control the spread of helmintic parasite infections. These anthelmintic agents generally function by destroying helmintic parasites in various developmental stages including adults, larvae, and eggs. Many of these compounds, however, are toxic to the host in effective dosages, difficult to prepare or synthesize, expensive, or produce adverse side effects when administered to the host animal. There exists, therefore, a continuing need for new and more effective methods for controlling helmintic parasites.
Previous methods for controlling helmintic parasites include the following: U.S. Pat. Nos. 3,390,148 discloses the use of thioimidates as anthelmintic agents. 3,458,633 discloses the use of thiazoline derivatives as anthelmintic agents. 3,915,986 discloses the use of 5-propylthio-2-benzimidazole carbamate against gastro-intestinal parasites in animals. 3,721,740 discloses the use of phenylhydrazone derivatives as anthelmintic agents. 4,175,135 discloses a method for controlling acarina ectoparasites using 2-aryl-1,3-cyclohexanedione. 4,255,447 discloses the use of phenylcyclopropane carboxycylic acid derivatives having acaracidal properties. 4,299,837 discloses using benzimidazole-carbamates as anthelmintic agents. 4,468,390 discloses anthelmintic compositions comprising antibiotics, benzimidazole, salicylamide, and isoquinoline compounds. 4,105,779 discloses oral anthelmintic compositions comprising phosphate compounds and thermoplastic resins. 4,287,176 discloses using thermally revisable gels containing levamisole, tetramisole, butamisole and benzamisole. 4,348,389 discloses administering substituted quinoxaline adducts to infested animals to control parasitic worms. 4,337,274 discloses flukicidal diphenylether compounds. 4,593,024 to Lu et al. discloses dihydroisoxazole compounds having anthelmintic properties. 4,009,266 discloses a method for controlling gastro-intestinal nematode parasites in domestic animals. 3,978,060 discloses new compounds used to eradicate internal parasites. 3,980,791 discloses pour-on tetramisole and levamisole anthelmintic compositions.
The RAL compounds of the present invention are known compounds. Preparation of the RAL compounds of the present invention, zearalenone, zearalanone, zearalene, zearalane, zearalenol, zearalanol, and dideoxyzearalane, are disclosed in U.S. Pat. Nos. 3,196,019, 3,239,354, 3,239,341, 3,239,348, 3,239,345, and 3,453,367, all incorporated herein by reference. The compounds are used as growth promotants in animals.